Solid state lighting devices are used for a number of lighting applications. For example, solid state lighting panels including arrays of solid state lighting devices have been used as direct illumination sources, for example, in architectural and/or accent lighting. A solid state lighting device may include, for example, a packaged light emitting device (LED) including one or more light emitting diode chips. Inorganic LEDs typically include semiconductor layers forming p-n junctions. Organic LEDs (OLEDs), which include organic light emission layers, are another type of solid state light emitting device. Typically, a solid state light emitting device generates light through the recombination of electronic carriers, i.e. electrons and holes, in a light emitting layer or region. LED chips, or dice, can be mounted in many different ways for many different applications. For example, an LED chip can be mounted on a header and enclosed by an encapsulant for protection, wavelength conversion, focusing, dispersion/scattering, etc. LED chips can also be mounted directly to a submount, such as a PCB, and can be coated directly with a phosphor, such as by electrophoresis or other techniques. Accordingly, as used herein, the term “light emitting diode” or “LED” can refer to an LED chip, including an LED chip coated or otherwise provided with phosphor, or to a packaged device, such as a packaged device that includes an LED chip and that provides electrical contacts, primary optics, heat dissipation, and/or other functional features for the LED chip.
Recently solid state lighting systems have been developed for general illumination applications. The design of a solid state lighting system for general illumination typically involves designing optical, power and thermal management systems in order to provide a particular level of performance with respect to lumen output, power requirements and junction temperature of Light Emitting Diode (LED) light sources. The junction temperature of LEDs may be important as it may be a contributing factor in the lifetime of the LEDs. In particular, if the junction temperature exceeds the recommended junction temperature of the manufacturer, then the LEDs will typically not achieve the lifetime rated by the manufacturer. Furthermore, as the operating temperature of LEDs changes, the current through the LEDs may change. For this and other reasons, changes in operating temperature can result in color shifts in the resulting light output. Maintaining a stable operating temperature may, therefore, also benefit in maintaining stable color output of a solid state light source.
Thermal management for solid state lighting systems has generally fallen into two categories: passive systems and active systems. These systems have typically been integral to the lighting device. Thus, for example, the LR6 recessed downlight from Cree LED Lighting Solutions of Morrisville, N.C., utilizes a passive system that incorporates a heat sink that is exposed to the room in which the LR6 is mounted. Thus, the LR6 provides not only the light source but also the trim for a recessed fixture in which the LR6 is mounted. By exposing the heat sink to the room the LR6 benefits from any air currents that break the boundary layer between the heat sink and the air in the room. Breaking the boundary layer between a heat sink and its environment can increase the efficacy of the heat sink, thereby lowering the junction temperature of the LEDs.
Active thermal management for solid state lighting systems has also been utilized. For example, U.S. Pat. No. 7,144,135 entitled “LED Lamp Heat Sink” describes an LED lamp that includes a fan that moves air over a heat sink. Additionally, LED downlights with integral synthetic jet cooling systems have also been announced by Nuventix and Philips. See nuventix.com/news/Nuventix-Announces-SynJet-Fanless-Air-Cooler-for-Philips-Fortimo-LED-Downlight-Module date Apr. 7, 2008 on the World Wide Web. However, current solutions may rely on specifically designed fixtures, structures and/or environments. In this regard, thermal management solutions corresponding to LED modules that may be provided for inclusion in products/devices manufactured by third parties may be inadequate and/or unascertainable.